Preparation of a Decagonal Al–Cu–Co Single Quasicrystal by the Czochralski Method

Abstract

Production of several phase diagrams including a decagonal(d-) phase in Al–Cu–Co alloy system was investigated to reveal the composition of the liquid in equilibrium with the stoichiometric Al₆₅Cu₁₅Co₂₀ d-phase as objective phase. The d-quasicrystal is only formed through the peritectic reaction between primary crystalline cubic phase and liquid phase. In order to avoid the peritectic reaction, the molten alloy composition was collected Al_63.9Cu_28.2Co_7.9 in the crucible which composition equilibrates to the Al₆₅Cu₁₅Co₂₀ d-solid phase at 1173 K with the condition of the Czochralski method. As a result, we have succeeded in the production of a single decagonal quasicrystal, 30 mm in length and 1 to 5 mm in diameter, with a mean composition of about Al₆₅Cu₁₅Co₂₀.